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Reverse Pairs (hard)
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Problem Statement

Examples

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Problem Statement

Given an array of integers nums, return the count of reverse pairs in the array.

A reverse pairis a pair (i, j) where:

  • 0 <= i < j < nums.length and
  • nums[i] > 2 * nums[j].

Examples

  • Example 1:

    • Input: nums = [4, 3, 4, 1]
    • Expected Output: 3
    • Justification: The three reverse pairs are (0, 3), (1, 3) and (2, 3).

  • Example 2:

    • Input: nums = [4, 1, 2]
    • Expected Output: 1
    • Justification: There is only one reverse pair (0, 1) since 4 > 2 * 1.

  • Example 3:

    • Input: nums = [6,5,4,3,2,1]
    • Expected Output: 6
    • Justification: The siz reverse pairs are (0, 4), (0, 5),(1, 4), (1, 5), (2, 5) and (3, 5).

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Try solving this question here:

Python3
Python3
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On this page

Problem Statement

Examples

Try it yourself